Temporarily enable staging branch for abi check test

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
Change-Id: I42aacdfe175865ceb0a74d940a8d192fe9fa482f
diff --git a/mbed-tls-restricted-pr-ci-testing.yaml b/mbed-tls-restricted-pr-ci-testing.yaml
index ec48dbe..a2886ff 100644
--- a/mbed-tls-restricted-pr-ci-testing.yaml
+++ b/mbed-tls-restricted-pr-ci-testing.yaml
@@ -46,7 +46,7 @@
         repo: mbedtls-restricted
         branch-discovery: all
         discover-pr-origin: both
-        head-filter-regex: 'dev/dgreen-arm/ci-testing-development|PR-(758|759|806|850|906|916|919|1225|1227|1233|1357|1358)-.*'
+        head-filter-regex: 'dev/dgreen-arm/ci-testing-development|PR-(758|759|806|850|906|916|919|1225|1227|1233|1357|1358)-.*|PR-1428-merge'
         status-checks:
           skip: true
           skip-branch-source-notifications: true